1. Field of the Invention
The present invention relates to an insulator of varying density for a wheel suspension system. The present invention further includes a method of deforming the insulator to densify and to shape a portion of the insulator.
2. Description of the Related Art
A wheel suspension system for a vehicle includes a support structure having an aperture and adapted to be mounted to the vehicle. A piston rod of a damper tube or shock absorber is at least partially disposed within the aperture and is displaceable relative to the support structure along a line of travel. A plate is mounted to the piston rod and moves relative to the support structure during the displacement of the piston rod. An insulator is compressibly disposed between the support structure and the plate.
The insulator is formed of an elastomeric material of a first density and presents an exterior surface adjacent at least one of the support structure and the plate. When the piston rod is displaced along the line of travel, the support structure and the plate move relative to each other to load and unload force to the insulator. The insulator compresses and decompresses between the plate and the support structure to absorb loads and vibration between the plate and the support structure. The insulator has a tendency to become cracked and/or cut as the insulator is repeatedly loaded and unloaded because the force delivered by the support structure and the plate to the insulator causes localized stress, i.e., concentrated stress, on the exterior surface of the insulator. The cracks and/or cuts propagate with repeated loading and unloading of the insulator. The cracks and/or cuts degrade the vibration dampening characteristics of the insulator and degrades the durability and reliability of the insulator.
U.S. Pat. No. 6,592,112 to Bishop et al. (the '112 patent) discloses a channel defined by the exterior surface and extending into the elastomeric material for reducing the cracking and cutting of the insulator by the support structure and the plate. The insulator deforms when the support structure and the plate exert a compressive force on the insulator. The channel allows the insulator to deform in a manner such that the localized stress on the exterior surface of the insulator is distributed along the exterior surface. Because the channel reduces the cracking and/or cutting of the insulator, the channel increases the durability and reliability of the insulator. However, as the support structure and the plate exert a compressive force on the insulator, the insulator flexes about the channel and cracks at a bottom of the channel. Although the channel reduces cracking, a further reduction or elimination of cracking would advantageously increase the durability and reliability of the insulator.
One way to decrease the flexibility of the insulator about the channel is to increase the density of the insulator. The density of the elastomeric material is increased for decreasing the flexibility of the insulator about the channel such that the flexing of the insulator about the channel is limited and to strengthen the material about the channel to reduce cracking at the bottom of the channel. However, increasing the density of the elastomeric material of the insulator disadvantageously limits the ability of the insulator to absorb loads and vibrations between the support structure and the plate. In other words, the density of the entire insulator is increased, which limits the cracking about the channel but which also disadvantageously reduces the load and vibration absorption capabilities of the insulator.
Accordingly, it would be desirable to manufacture an insulator for a wheel suspension system that is resistant to cracking and/or cutting of the insulator caused by the support structure and/or the plate while still maintaining desirable load and vibration absorption capabilities. Likewise, it would be desirable to identify a method of forming the insulator with such characteristics.